Fungus Diseases of Fruiting Plants
How diseases spread Sanitation is essential in the prevention and control of Sanitation is essential in the prevention and control of diseases in the landscape!
Fungus Diseases Anthracnose Armillaria Root Rot (Oak Root Fungus) Botrytis (Gray Mold) Brown Rot Coryneum Blight of Stone Fruits (Shot-Hole Fungus) Eutypa Dieback Peach Leaf Curl Powdery Mildew Phytopthora th Fruit Rot Phytopthora Gummosis Phytopthora Root Rot Rust Scab Sooty Mold Verticillium
Fruiting Plants Affected by Avocado Banana Citrus Fig Mango Papaya Pomegranate Anthracnose
Fruiting Plants Affected by Anthracnose Anthracnose is the primary reason why mangoes, avocadoes and some other fruit trees develop blackened fruit that drops prematurely. Anthracnose is a fungal disease that is exacerbated by rain and high humidity. During dry weather the disease is virtually absent. Anthracnose symptoms can develop on flowers, fruit, leaves, or twigs. Infected fruit is the most serious concern, but most fruit damage does not develop until after harvest. Unhealthy or dead leaves are the most obvious symptom in groves. Spots form on leaves, beginning g as yellow, then brown discolorations that coalesce into large dead areas. Necrosis occurs across or between leaf veins, on leaf margins, and most often at leaf tips. If disease is severe trees drop many leaves prematurely New shoots can If disease is severe, trees drop many leaves prematurely. New shoots can develop brown or purplish lesions, and shoots may dieback. Infected flower heads can turn dark and die without producing fruit, or young fruit may form and then drop.
Fruiting Plants Affected by Anthracnose Extended foggy or rainy conditions and mild winter temperatures, and where many dead leaves and twigs and mummified fruit accumulate in trees, anthracnose can produce enough spores to cause a disease problem. Spores spread in splashing water and can cause infection anytime from fruit set to harvest. Once infected fruit starts to ripen, temperatures of 75 F and above will accelerate anthracnose development, while temperatures below 59 F retard disease development. After harvest, lesions become blacker, larger, and increasingly sunken. Lesions eventually spread over the entire fruit surface and throughout pulp. p When the fruit is cut in half through one of the lesions, rot extending into the flesh often exhibits a hemispherical pattern. Decayed pulp initially is firm, but becomes soft and putrid as decay advances. Control anthracnose primarily with good cultural practices in the grove and proper preharvest and postharvest fruit handling. Prune out dead limbs and twigs where fungi sporulate. If many dead leaves are entwined in the canopy, knock them out of the tree. Prune low limbs to at least 2 feet off the ground to reduce humidity within canopies by improving air circulation.
Anthracnose disease cycle
Fruiting Plants Affected by Armillaria i Root Rot Apple pp Avocado Citrus Caneberries Fig Grape Olive Pear Stone Fruit (Genus Prunus) And Others
Fruiting Plants Affected by Armillaria Root Rot Armillaria root rot is one of many micro-organisms that naturally decay stumps and roots of trees. But Armillaria can also attack living trees. Armillaria thrives under moist conditions The fungus can survive for many years in dead or living tree roots. As the fungus grows through the soil, they branch and penetrate roots, causing new infections. In addition to direct root contact, fungus rhizomorphs are the principal means of tree-to-tree spread. Armillaria root rot can develop slowly, and symptoms may not appear until the fungus is well established. Often, trees killed by Armillaria i have first been weakened by some other agents such as insects or other pathogens. The best strategy for preventing armillaria root rot on ornamental trees and shrubs is to promote the vigor of the plants. Avoid injuring trees and avoid damaging or stressing the roots.
Fruiting Plants Affected by Botrytis (Gray Mold) Caneberries Citrus Grape Guava Lemon Stone Fruit (genus Prunus) Strawberry Many others
Fruiting Plants Affected by Botrytis Gray Mold Botrytis cinerea Botrytis causes light tan to grayish lesions with gray spores. Spore masses may grow on the rotted areas. Fruit becomes more susceptible as it ripens. Botrytis-diseased fruit usually do not remain on the tree until next season, but they are present as inoculum sources for the current season's crop. Botrytis can infect uninjured ripening fruit and cause green fruit rot and incipient infections of young fruit. Wetness, either rain or dew, and injury or fruit cracking increases preharvest infection and consequent rot. Practices which increases air circulation such as pruning with thinning cuts and fruit thinning help to reduce or prevent this disease.
Fruiting Plants Affected by Brown Rot Citrus Stone Fruit (Apricot, Cherry, Nectarine, Peach, & Plum)
Fruiting Plants Affected by Brown Rot Pathogens: mostly Monilinia fructicola and M. laxa Ripe fruit rot caused by Monilinia results in firm, circular spots that spread rapidly over fruit. Monilinia causes dark brown lesions on fruit that eventually turn black from the development of pseudosclerotia (fungal tissue), Fruit with brown rot infections are shriveled and develop powdery tan masses of spores. Individual fruit may be infected, but rotted fruit usually occur in clusters that are stuck together. Injured fruit and fruit that touch each other are the most susceptible to brown rot infections. When Monilinia-diseased fruit remain on the tree, they are known as mummies. Removing or turning under thinned fruit helps reduce fruit brown rot. Thinned fruit can be a source of inoculum for brown rot on ripening fruit, especially if they are left where they will come in contact with irrigation water. Fungicides are preventive, not eradicative; they must be applied to uninjured fruit before infections occur. Injured fruit cannot be protected from rot caused by Monilinia
Brown Rot Disease Cycle
Fruiting Plants Affected by Coryneum Blight (Shot-Hole Fungus) Apricot Cherry Nectarine Peach Plum
Coryneum Blight (Shot-Hole Fungus) Shot hole, or Coryneum blight, is a serious disease of almonds, apricots, nectarines, peaches and plums in California. i Reddish or purplish brown spots about 0.10 inch in diameter occur on new leaves and shoots. The spots expand and their centers turn brown. Tiny, dark specks sometimes form in the center of lesions, especially on leaves. Spots on young leaves have a narrow, light green or yellow margin and their centers often fall out as leaves expand, leaving "shot holes." Buds of peach, nectarine, and sometimes apricot are killed in the winter. Fruit may become rough and corky. Spotting occurs on the upper surface. Concentric lesions may develop on branches. The fungus that causes shot hole survives the dormant season inside infected buds and in twig lesions. The spores produced on lesions can remain alive for several months. They are spread by splashing rain or irrigation water. Spores that land on twigs, buds, blossoms, or young leaves require 24 hours of continuous wetness to cause infection. Only the current season's growth is susceptible to infection.
Coryneum Blight (Shot-Hole Fungus) Disease Cycle In California, twig and bud I C lif i t i d b d infections can occur during rainy weather any time between fall and spring. The fungus can germinate and dinfect at ttemperatures t as low as 36 F. Diligent sanitation and water management can provide adequate control where the incidence of shot hole is low. Avoid overhead sprinklers or use a low angle to avoid wetting foliage. Also, some varieties may be less susceptible. Where disease incidence is high, fungicides may be applied. On peaches and nectarines, a dormant spray will work well.
Apricot Apricot Eutypa Dieback Pathogen: Eutypa lata
Apricot Eutypa Dieback Pathogen: Eutypa lata Eutypa dieback, also known as Cytosporina, gummosis, and limb dieback, causes limbs or twigs to wilt and die suddenly in late spring or summer with the leaves still attached. The bark has a dark discoloration with ambercolored gumming; infected areas in the interior of the wood are discolored brown. This fungus infects fresh pruning wounds when rainfall occurs 2 to 6 weeks after pruning. While infections can occur at any time of the year during rainy periods, the greatest incidence is in fall and winter. Remove infected limbs at least 1 foot below any sign of the disease. The preferred control method is to prune during July and August after harvest. Ideally, pruning should be completed at least 6 weeks before the first rains. If pruning wounds are made outside of the preferred pruning period of July/August, use a fungicide to treat the wounds. Pruning during the summer months may encourage bark boring insects.
Fruiting Plants Affected by Peach Leaf Curl Nectarine Peach
Fruiting Plants Affected by Peach Leaf Curl Taphrina deformans Peach leaf curl affects the blossoms, fruit, leaves, and shoots of peaches and nectarines, and is one of the most common disease problems for backyard gardeners. When severe, the disease can reduce fruit production substantially. Leaf curl first appears in spring as reddish areas on developing leaves. These areas become thickened and puckered, causing leaves to curl and severely distort. The thickened areas turn yellowish gray and velvety as spores are produced on the surface by the leaf curl fungus. Affected leaves later turn yellow or brown and can remain on the tree or may fall off; they are replaced by a second set of leaves that develop more normally unless wet weather continues. The loss of leaves and the production of a second set result in decreased tree growth and fruit production. In addition, defoliation in spring may expose branches to sunburn injury. The leaf curl pathogen also infects twigs and shoots. Affected shoots become thickened, stunted, distorted, and often die. Only rarely do reddish, wrinkled areas develop on fruit surfaces; later in the season these infected areas become corky and tend to crack. If leaf curl infection builds up and is left uncontrolled for several years, the tree may decline and need to be removed. It takes about 2 weeks after leaves emerge from buds before leaf symptoms appear.
Fruiting Plants Affected by Peach Leaf Curl Taphrina deformans The fungus survives the hot, dry summer on the tree s surfaces.. In spring, the fungus is moved by splashing water and can infect newly developed leaves. To prevent peach leaf curl, treat peach and nectarine trees every year after leaves have fallen. Copper-based fungicides, calcium polysulfides, or synthetic fungicides can be used. To be effective, copper-containingcontaining compounds must have at least 50% copper. It is be advisable to apply a second treatment in spring, preferably before buds begin to swell, but definitely before budbreak (when green color is first visible). Although symptoms of leaf curl are seen primarily in spring as new leaves develop, there is little you can do to control the disease at this time. Normally, diseased leaves fall off within a few weeks and are replaced by new healthy leaves unless it is rainy. Development of leaf curl ceases when young tissue is no longer developing or when weather turns dry and warm (80 to 85 F). If leaf curl symptoms occurred on your trees in spring, be sure to treat the following fall, around late November, to prevent more serious losses the next year.
Disease Cycle of Peach Leaf Curl
Fruiting Plants Affected by Powdery Mildew Apple Caneberries Grape Mango Papaya Quince Stone Fruit Strawberry
Fruiting Plants Affected by Powdery Mildew Powdery mildew is a common disease on many types of fruiting plants. Different powdery mildew fungi cause similar diseases on different plants. Powdery mildew fungi generally do not require moist conditions to establish and grow, and normally do well in warm climates. Thus powdery mildews are more prevalent than many other diseases in California's dry summer weather. The disease can be serious on grapevines, caneberries, and fruit trees where it attacks new growth including buds, shoots, and flowers as well as leaves. New growth is dwarfed, distorted, and covered with a white, powdery growth. On apple, grape, apricot, nectarine, and peach, young fruits develop weblike russetted scars and sometimes develop a rough corky skin. Grapes with a severe infection may also crack or split and fail to grow and expand. Powdery mildew spores are carried by wind to new hosts. Moderate temperatures and shady conditions are generally the most favorable for powdery mildew development. Spores and mycelium are sensitive to extreme heat and direct sunlight. The best method of control is prevention. Avoiding the most susceptible varieties and p g p following good cultural practices will adequately control powdery mildew in many situations. However, where conditions are favorable, susceptible fruit trees and berries may require protection with fungicide sprays.
Phytophthora Gummosis on Citrus
Phytophthora Gummosis on Citrus An early symptom of Phytophthora gummosis is sap oozing from small cracks in the infected bark, giving the tree a bleeding appearance. The gumming may be washed off during heavy rain. The bark stays firm, dries, and eventually cracks and sloughs off. Lesions spread around the circumference of the trunk, slowly girdling the tree. Decline may occur rapidly within a year, especially under conditions favorable for disease development, or may occur over several years. Keep trunk dry; do not allow sprinkler water to hit it. Scrape away all diseased bark and a buffer strip of healthy light brown to greenish bark around margins. Allow to dry. Repeat if infection recurs.
Apple Avocado Fruiting Plants Affected by Caneberries Citrus Papaya Stone Fruit Many others Phytopthera h Root Rot
Phytopthera Root Rot Phytophthora root rot is the most serious avocado disease. The causal agent, Phytophthora cinnamomi, has over 1,000 hosts, including many species of annual flower crops, berries, deciduous fruit trees, ornamentals, and vegetables. Foliar symptoms of avocado root rot include small, pale green or yellowish leaves. Leaves often wilt and have brown, necrotic tips. Foliage is sparse and new growth is rare. There may be little leaf litter under infected trees. Small branches die back in the tree top, exposing other branches and fruit to sunburn because of the lack of shading foliage. Fruit production declines, but diseased trees frequently set a heavy crop of small fruit. Small, fibrous feeder roots are scarce at advanced stages of this disease. Where present, small roots are black, brittle, and dead from infection. Foliage is wilted even when soil under diseased trees is wet. Affected trees will decline and often die either rapidly or slowly. Root rot thrives in areas of excess soil moisture and poor drainage. Trees of any size and age may be affected.
Phytopthera Root Rot The pathogen is easily spread through movement of contaminated nursery stock of avocado and other plants, on equipment and shoes, in seed from fruit lying on infested soil, or by any activity by people or animals that moves moist soil from one place to another. Phytophthora spores spread easily and rapidly in water moving over or through the soil. Entire areas can readily become infested. Phytophthora species are not true fungi but have many fungal-like like attributes. Mulching promotes development of beneficial microorganisms antagonistic to Phytophthora cinnamomi and reduces the adverse effects of saline soil and water. Gypsum supplies calcium, which suppresses the formation of Phytophthora spores. Certain phosphites (phosphorous acid and phosphonate compounds) can markedly improve trees' ability to tolerate, t resist, or recover from infection by Phytophthora hth cinnamomi. Good control requires using fungicides in combination with other recommended practices, such as careful irrigation practices and applying wood chip mulch. Phosphites cannot eradicate Phytophthora from the grove and avocado root rot requires ongoing management throughout the life of the trees.
Phytopthera Fruit Rot Avocado Cherimoya Cherry Walnut Diseased fruit have a distinct circular black area that usually occurs near the bottom or lowest spot on the fruit. Internally, the rot extends into the flesh, darkening it in the same pattern as on the affected surface. Affected fruit are often touching the soil or are hanging on low branches. Most damage occurs within 3 feet of the ground. Phytophthora fruit rot is caused by Phytophthora spp., usually P. citricola, Most damage occurs after prolonged wet conditions, the same situation that favors anthracnose. In contrast to anthracnose, which is primarily a postharvest problem, Phytophthora fruit rot infections often become obvious while fruit is still hanging on the tree, as well as causing decay after harvest. The most common cause of infection is believed to be the splashing of Phytophthora propagules from the soil surface to the fruit during heavy rain or sprinkler irrigation. Prune lower limbs so they are 2 to 3 feet from the ground. Maintain a thick layer of mulch to hasten decomposition of fungi on soil. Consider removing and disposing of fruit lying on the ground because the fungus sporulates on dropped fruit.
Fruiting Plants Affected by Rust Caneberries Nectarine Peach The fungus survives in twig cankers or on other host parts. Airborne spores depend on wetness for infection. Infections of young twigs and leaves are the most common symptoms, but in California, fruit infections may be a major component of the disease as well.
Fruiting Plants Affected by Rust Fruit symptoms may resemble damage caused by stink bugs; confirm rust by the presence of rust spores within the fruit lesion or by leaf or twig symptoms. Twig cankers are the first symptoms of the disease in spring. Cankers develop after petal fall on 1-year-old fruiting wood. They appear as blisters and longitudinal splits in the bark about 0.12 to 0.25 inches long. They can most easily be seen using a 20X hand lens. Leaf lesions usually develop after cankers form in spring and may continue to develop through summer and into fall. The lesions appear as bright yellow, angular spots on the upper surface of leaves. The lower surface of the leaves contains brown spore masses. A high incidence of early leaf infections may cause midseason defoliation and numerous fruit infections at harvest. Early and severe defoliation also may reduce yields and stimulate the production of new leaves and buds late in the growing g season. Fruit lesions may develop during the growing season after leaf symptoms. They first develop as small, brownish spots (0.1 inch) with green halos on mature, yellow fruit. When fruit reddens, lesion halos become greenish yellow. The lesions are sunken and extend several millimeters into the fruit. In orchards where rust develops it is managed with a fungicide treatment in spring.
Fruiting Plants Affected by Scab Apple Peach Pear
Fruiting Plants Affected by Scab Pathogen: Venturia spp. Scab is most severe in coastal areas where spring and early summer weather is cool and moist; however, it can be a problem wherever apples are grown when conditions are favorable for its development. Scab first appears as velvety, dark olive-to-black spots on fruit, leaves, and stems. On leaves, infections cause leaf puckering and twisting and eventually tear with age. When infections occur early, fruit spots become scablike with age and the fruit may become misshapen. Secondary infections that occur later in the season appear as black, velvety pinpoint spots on fruit and leaves. The pathogen overwinters primarily in infected leaves on the ground. Primary spores are discharged from fuiting bodies on dead leaves during spring rains and infect young leaves and fruit during periods of prolonged moisture. These infections produce secondary spores, which may cause further spread of disease during wet periods. Overwintering twig lesions from secondary infections may also be an important source of innoculum in spring. Infection occurs most rapidly between 55 and 75 F and leaves or fruit must remain wet continuously for a minimum of 9 hours for infection to occur. Scab can destroy a crop. Young infected flowers or fruit may drop or the fruit may become malformed and unsightly, rendering them unusable. Defoliation follows severe early leaf infection. Late-season infections, which cause small "pinpoint" infections, generally can be tolerated in backyard trees because peeling fruit removes the scabs, and fruit are less likely to be deformed.
Disease Cycle of Scab
Sooty Mold Sooty Mold is a fungus which grows on the honeydew produced by many sucking insects including: aphids, mealybugs, psyllids, some scale insects, & whitefly.
Fruiting Plants Affected by Almond Avocado Caneberries Chestnut Mango Olive Pistachio Stone Fruit Verticillium illi Wilt
Fruiting Plants Affected by Verticillium Wilt Verticillium wilt causes the foliage to turn faded green, yellow, or brown, and sometimes wilt in scattered portions of the canopy or on scattered branches. Shoots and branches wilt and die, often beginning on one side of the plant, and occasionally entire plants die. Peeling back the bark on newly infected branches may reveal dark stains following the grain on infected wood. This discoloration is a common field diagnosis symptom for most woody plants infected by Verticillium wilt. The disease is most prevalent during periods of cool, wet weather. Keep plants vigorous by providing trees with proper irrigation, fertilizer, and other appropriate care to promote new growth and increase their chance for survival.